A resolver is a rotary transformer comprising a rotor and a stator with one or more windings (i.e., coils). In response to excitation by one or more source signals, the windings output one or more sine (sin) or cosine (cos) signals (i.e., output voltages). The magnitude and phase of the sin and cos signals are used to determine the angular position of a resolver shaft.
Typically, a multi-pole resolver is used for high resolution applications. A multi-pole resolver houses multiple sin/cos pole windings in the stator and thus provides more accuracy than a basic resolver. Unfortunately, multi-pole resolvers have a more complex physical structure than basic revolvers. Since sin(θ), sin(θ+180), cos(θ), and cos(θ+180) pole windings share a common resolver core, magnetic flux interference among the poles increases as resolver rotation speed increases. The magnetic flux interference distorts the sin and cos output signals and breaks their orthogonality, which results in decreased accuracy of angular position measurements.